This study provides new experimental evidence for the disconnection of the lamellar phase (L-alpha) in pseudobinary water-non-ionic surfactant systems. To prove that the disconnection is indeed a general phenomenon the phase behavior of the pseudobinary system water-pentaethylene glycol doclecyl ether/hexaethylene glycol dodecyl ether (H2O-C12E5/C12E6) was investigated as a function of the surfactant composition 3 and the total surfactant concentration gamma. At a fixed gamma of 0.10 the extension of the highly diluted L-alpha phase shrank continuously with increasing amount of C12E6, i.e., increasing delta, until it disappeared at delta = 0.60. The gamma - T phase diagram of this particular surfactant mixture was found to have a disconnected L-alpha phase. For the first time, SAXS measurements were carried out to monitor structural changes related to the disconnection. For this purpose the interlayer spacing d and the effective cross-sectional area as were determined from the SAXS data along characteristic paths through the L-alpha phase. (c) 2006 Elsevier Inc. All rights reserved.